1. Field of the Invention
The present invention relates to disc brake mechanisms and, more specifically, to a mechanism featuring a load plate configured to optimize the distribution of lining/rotor contact pressure.
2. Description of the Related Art
The present invention is particularly applicable to a disc brake assembly of the type which includes a rotor mounted for rotation with a vehicle wheel and a caliper straddling the periphery of the rotor. Friction pads are carded by the caliper on opposite sides of the rotor and are movable into contact with oppositely disposed friction surfaces of the rotor by actuating means driven by an air actuator. In a caliper disc brake, each friction pad is located intermediate one leg of the caliper and the adjacent friction surface of the rotor. The actuating mechanism is usually carried by one leg of the caliper and serves to move the friction pad adjacent to that leg axially into contact with the rotor. The reaction force of such contact draws the other leg of the caliper and the other friction pad into contact with the opposite surface of the rotor. Although various arrangements are known for applying force to fiction pads within a disc brake assembly, most impart the force directly to a backing plate defined as a flat semi-rigid structure. Some cases utilize a single piston, whereas others impart the force using dual annularly displaced pistons. In either case the lack of stiffness in the structure of the backing plate and the concentration of piston force at the region of contact results in a nonuniform pressure distribution causing peak forces in the friction material. As a result, nonuniform pressure distribution produces ineffective use of lining material such that the full effectiveness of the lining/rotor contact may not be realized. Therefore, there is a need for a disc brake assembly which applies force to a friction pad through a structurally stiff member that provides uniform pressure distribution between the lining and the rotor.